Dexterous in performing an action, so as to escape notice; nimble; skillful; cautious; shrewd; knowing; -- in a good sense.
- Clever or cunning, especially in the practice of deceit.
- Stealthy or surreptitious: took a sly look at the letter on the table.
- Playfully mischievous: a sly laugh.
- on the sly In a way intended to escape notice: took extra payments on the sly.